Image pickup element and image pickup device

ABSTRACT

An image pickup element includes a light-receiving portion having a matrix arrangement formed by disposing first-direction arrays, each having photoelectric conversion portions arranged in a first direction with a predetermined gap maintained therebetween, in a second direction orthogonal to the first direction, and micro-lenses provided above the light-receiving portion. A certain first-direction array in the matrix arrangement is provided with a pair of photoelectric conversion portions that optically receive, via a pair of micro-lenses, photographic-subject light beams passing through a pair of segmental regions in an exit pupil of a photographic optical system, the pair of segmental regions being disposed biasedly in opposite directions from each other in the first direction. The pair of micro-lenses is disposed such that light axes thereof extend through vicinities of edges of the pair of photoelectric conversion portions, the edges being the farthest edges from each other in the first direction.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. JP 2009-002326 filed in the Japanese Patent Office on Jan. 8, 2009,the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the technology of image pickup elementscapable of optically receiving photographic-subject light beams passingthrough exit pupils of photographic optical systems.

2. Description of the Related Art

In image pickup devices, such as single-lens reflex cameras withinterchangeable lenses, image pickup elements capable of performingfocus detection based on a phase-difference detection method are used.An image pickup element of this type will sometimes be referred to as“image pickup element having a phase-difference detecting function”hereinafter. Specifically, in an image pickup element having aphase-difference detecting function, a pair of photoelectric conversionportions (photodiodes) that generate pixel signals by opticallyreceiving photographic-subject light beams passing through a pair ofsegmental regions (for example, left and right pupil segments) in anexit pupil of an interchangeable lens (photographic optical system) isprovided in a plurality. The following are examples of such image pickupelements of the related art.

For example, Japanese Unexamined Patent Application Publication No.2001-250931 discloses an image pickup element having a phase-differencedetecting function, in which bisected-like photoelectric conversionportions (referred to as “half-sized photoelectric conversion portions”hereinafter) are provided in each of normal pixels (R, G, and B pixels)that acquire image signals of a photographic subject. In other words, apair of half-sized photoelectric conversion portions is disposed beloweach micro-lens.

Japanese Unexamined Patent Application Publication No. 2005-303409discloses another example of an image pickup element having aphase-difference detecting function, which limits photographic-subjectlight with small openings in a light-blocking mask made of a metalliclayer in a pair of neighboring pixels so as to optically receive a pairof segmental regions in the exit pupil with a pair of photoelectricconversion portions.

SUMMARY OF THE INVENTION

However, in the image pickup element according to Japanese UnexaminedPatent Application Publication No. 2001-250931, it may be necessary toinstall a transistor, which is for converting the output from eachhalf-sized photoelectric conversion portion to an electric signal, nearthe photoelectric conversion portion. This means that the photoelectricconversion portion is reduced in size by an amount equivalent to theinstallation space for the transistor and thus lowers the amount oflight that can be received by the photoelectric conversion portion(i.e., the sensitivity of the photoelectric conversion portion). Thismakes it difficult to accurately perform focus detection based on aphase-difference detection method.

On the other hand, in the image pickup element according to JapaneseUnexamined Patent Application Publication No. 2005-303409, since thephotographic-subject light is limited using a small opening in thelight-blocking mask for each pixel, further size reduction of theopenings in the light-blocking mask is desired as pixels becomeminiaturized with an increase in pixels in image pickup elements.However, there is a possibility that formation of such openings may bedifficult in view of manufacture.

It is desirable to provide an image pickup element having aphase-difference detecting function that is capable of accuratelyperforming focus detection based on a phase-difference detection methodand that can be manufactured satisfactorily even as pixels becomeminiaturized.

According to a first embodiment of the present invention, there isprovided an image pickup element including a light-receiving portionhaving a matrix arrangement of photoelectric conversion portions, thematrix arrangement being formed by disposing a plurality offirst-direction arrays, each having photoelectric conversion portionsarranged in a first direction with a predetermined gap maintainedtherebetween, in a second direction that is orthogonal to the firstdirection, and a plurality of micro-lenses provided above thelight-receiving portion. A certain first-direction array in the matrixarrangement of photoelectric conversion portions is provided with a pairof photoelectric conversion portions that optically receive, via a pairof micro-lenses, photographic-subject light beams passing through a pairof segmental regions in an exit pupil of a photographic optical system,the pair of segmental regions being disposed biasedly in oppositedirections from each other in the first direction. The pair ofmicro-lenses is disposed such that light axes thereof extend throughvicinities of edges of the pair of photoelectric conversion portions,the edges being the farthest edges from each other in the firstdirection.

According to a second embodiment of the present invention, there isprovided an image pickup device including a photographic optical systemand an image pickup element configured to optically receivephotographic-subject light passing through an exit pupil of thephotographic optical system. The image pickup element includes alight-receiving portion having a matrix arrangement of photoelectricconversion portions, the matrix arrangement being formed by disposing aplurality of first-direction arrays, each having photoelectricconversion portions arranged in a first direction with a predeterminedgap maintained therebetween, in a second direction that is orthogonal tothe first direction, and a plurality of micro-lenses provided above thelight-receiving portion. A certain first-direction array in the matrixarrangement of photoelectric conversion portions is provided with a pairof photoelectric conversion portions that optically receive, via a pairof micro-lenses, photographic-subject light beams passing through a pairof segmental regions in the exit pupil, the pair of segmental regionsbeing disposed biasedly in opposite directions from each other in thefirst direction. The pair of micro-lenses is disposed such that lightaxes thereof extend through vicinities of edges of the pair ofphotoelectric conversion portions, the edges being the farthest edgesfrom each other in the first direction.

According to the embodiments of the present invention, the image pickupelement can accurately perform focus detection based on aphase-difference detection method and can be manufactured satisfactorilyeven as pixels become miniaturized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an external configuration of an image pickup deviceaccording to an embodiment of the present invention;

FIG. 2 also illustrates the external configuration of the image pickupdevice;

FIG. 3 is a vertical sectional view of the image pickup device;

FIG. 4 is a block diagram showing an electrical configuration of theimage pickup device;

FIG. 5 is a diagram for explaining the configuration of an image pickupelement;

FIG. 6 is another diagram for explaining the configuration of the imagepickup element;

FIG. 7 is a vertical sectional view for explaining the configuration ofnormal pixels;

FIG. 8 is a plan view for explaining the configuration of the normalpixels;

FIG. 9 is a vertical sectional view for explaining the configuration ofan AF sensor portion;

FIG. 10 is a plan view for explaining the configuration of the AF sensorportion 11 f;

FIG. 11 illustrates a simulation result obtained when a focal plane isdefocused towards the near side by 200 μm from an image pickup face ofthe image pickup element;

FIG. 12 illustrates a simulation result obtained when the focal plane isdefocused towards the near side by 100 μm from the image pickup face;

FIG. 13 illustrates a simulation result of an in-focus state in whichthe focal plane accords with the image pickup face;

FIG. 14 illustrates a simulation result obtained when the focal plane isdefocused towards the far side by 100 μm from the image pickup face;

FIG. 15 illustrates a simulation result obtained when the focal plane isdefocused towards the far side by 200 μm from the image pickup face;

FIG. 16 is a diagram for explaining a graph Gc showing the relationshipbetween a difference in barycentric positions between a pair of imagesequences and a defocus amount;

FIG. 17 is a diagram for explaining the configuration of an AF areaaccording to a modification of the embodiment of the present invention;

FIG. 18 is a diagram for explaining the configuration of an AF areaaccording to another modification of the embodiment of the presentinvention;

FIG. 19 is a diagram for explaining the configuration of an AF areaaccording to another modification of the embodiment of the presentinvention;

FIG. 20 is a diagram for explaining the configuration of an AF sensorportion according to a modification of the embodiment of the presentinvention;

FIG. 21 is a diagram for explaining an AF area having the AF sensorportions; and

FIG. 22 is a diagram for explaining the configuration of an AF sensorportion according to another modification of the embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment Configuration ofRelevant Portion of Image Pickup Device

FIGS. 1 and 2 illustrate an external configuration of an image pickupdevice 1 according to an embodiment of the present invention.Specifically, FIGS. 1 and 2 are a front view and a rear view,respectively.

The image pickup device 1 is, for example, a digital still camera of asingle-lens reflex type and includes a camera body 10 and aninterchangeable lens 2 serving as a photographic lens detachable to thecamera body 10.

Referring to FIG. 1, the front surface of the camera body 10 is providedwith a mounting portion 301 located substantially in the middle of thefront surface and to which the interchangeable lens 2 is fitted, a lensreplacement button 302 disposed to the right of the mounting portion301, and a grippable portion 303. The camera body 10 is provided with amode setting dial 305 disposed in an upper left section of the frontsurface, a control-value setting dial 306 disposed in an upper rightsection of the front surface, and a shutter button 307 disposed on theupper surface of the grippable portion 303.

Referring to FIG. 2, the rear surface of the camera body 10 is providedwith a liquid crystal display (LCD) 311, a setting-button group 312disposed to the left of the LCD 311, a cross keypad 314 disposed to theright of the LCD 311, and a push button 315 disposed in the center ofthe cross keypad 314. The rear surface of the camera body 10 is alsoprovided with an electronic viewfinder (EVF) 316 disposed above the LCD311, an eyecup 321 surrounding the EVF 316, and a main switch 317disposed to the left of the EVF 316. Moreover, the rear surface of thecamera body 10 is provided with an exposure correction button 323 and anautomatic-exposure (AE) lock button 324 disposed to the right of the EVF316, and a flash portion 318 and a connection terminal portion 319disposed above the EVF 316.

The mounting portion 301 is provided with a connector Ec (see FIG. 4)used for an electrical connection with the fitted interchangeable lens 2and a coupler 75 (see FIG. 4) used for a mechanical connection.

The lens replacement button 302 is a button to be pressed when detachingthe interchangeable lens 2 from the mounting portion 301.

The grippable portion 303 is a portion to be gripped by a user duringphotographic shooting using the image pickup device 1 and is providedwith protrusions and depressions that conform to the shape of the humanhand to enhance fittability. The grippable portion 303 contains abattery accommodating chamber and a card accommodating chamber (notshown). The battery accommodating chamber is configured to accommodate abattery 69B (see FIG. 4) serving as a power source for the camera,whereas the card accommodating chamber is configured to detachablyaccommodate a memory card 67 (see FIG. 4) for storing image data ofphotographic images. The grippable portion 303 may be provided with agrip sensor for detecting whether or not the grippable portion 303 isgripped by a user.

The mode setting dial 305 and the control-value setting dial 306 areeach formed of a substantially disk-shaped member that is rotatablewithin a plane substantially parallel to the upper surface of the camerabody 10. The mode setting dial 305 is provided for alternativelyselecting modes and functions included in the image pickup device 1,which include an automatic-exposure (AE) control mode and anautomatic-focus (AF) control mode, various shooting modes, such as astill-image shooting mode for shooting a single still image and acontinuous shooting mode for performing continuous shooting, and areproduction mode for reproducing a recorded image. On the other hand,the control-value setting dial 306 is provided for setting controlvalues for various functions included in the image pickup device 1.

The shutter button 307 is a press button that can be operated to ahalf-pressed state, in which the button is pressed halfway, and afully-pressed state, in which the button is pressed further downward.When the shutter button 307 is half-pressed in the still-image shootingmode, a preparatory operation (including setting of an exposure controlvalue and focus detection) for shooting a still image of a photographicsubject is executed. When the shutter button 307 is fully pressed, aphotographic shooting operation (a series of processes includingexposing an image pickup element 101 (see FIG. 3) to light andperforming predetermined image processing on an image signal obtained bythe exposure process so as to record the image in, for example, thememory card) is executed.

The LCD 311 includes a color liquid-crystal panel capable of performingimage display and is configured to, for example, display an image pickedup by the image pickup element 101 (see FIG. 3) or reproduce and displaya recorded image, as well as display a setting screen for functions andmodes included in the image pickup device 1. As an alternative to theLCD 311, an organic electroluminescence display unit or a plasma displayunit may be used.

The setting-button group 312 includes buttons for operating variousfunctions included in the image pickup device 1. The setting-buttongroup 312 includes, for example, a selection confirmation switch forconfirming the content selected on a menu screen displayed on the LCD311, a selection cancellation switch, a menu display switch forswitching the content on the menu screen, a display on/off switch, and adisplay enlargement switch.

The cross keypad 314 has an annular component including multiplepressable sections (i.e., sections denoted by triangular arrows in FIG.2) arranged at fixed intervals in the circumferential direction, and iscapable of detecting a pressing operation performed on one of thepressable sections in accordance with a corresponding one of contacts(switches) (not shown) provided to face the corresponding pressablesections. The push button 315 is disposed in the center of the crosskeypad 314. The cross keypad 314 and the push button 315 are providedfor changing the magnification (moving a zoom lens 212 (see FIG. 4) inthe wide-angle-end direction or the telephoto-end direction),frame-advancing recorded images reproduced on, for example, the LCD 311,and inputting commands for setting shooting conditions (including theaperture, shutter speed, and on/off mode of flash).

The EVF 316 includes a liquid crystal panel 310 (see FIG. 3) and isconfigured to display an image picked up by the image pickup element 101(see FIG. 3) or reproduce and display a recorded image. The EVF 316 orthe LCD 311 performs a live-view (preview) display operation fordisplaying a photographic subject in a video mode on the basis of imagesignals sequentially produced by the image pickup element 101 prior tothe actual shooting operation (i.e., a shooting operation for recordingan image) so as to allow the user to visually check the photographicsubject actually picked up by the image pickup element 101.

The main switch 317 is formed of a horizontally slidable switch havingtwo contacts. When the main switch 317 is set in the left position, theimage pickup device 1 is turned on, whereas when the main switch 317 isset in the right position, the image pickup device 1 is turned off.

The flash portion 318 is defined by a built-in flashlight of a pop-uptype. On the other hand, when an external flashlight, for example, is tobe attached to the camera body 10, the external flashlight is connectedusing the connection terminal portion 319.

The eyecup 321 is a C-shaped light-blocking member having light-blockingproperties for preventing penetration of external light into the EVF316.

The exposure correction button 323 is for manually adjusting exposurevalues (aperture and shutter speed). The AE lock button 324 is forfixing the exposure.

The interchangeable lens 2 functions as a lens window that takes inlight (optical image) from a photographic subject and also functions asa photographic optical system for guiding the photographic-subject lightto the image pickup element 101 disposed within the camera body 10. Thisinterchangeable lens 2 can be detached from the camera body 10 bypressing the lens replacement button 302.

The interchangeable lens 2 includes a lens group 21 (see FIG. 4)constituted by a plurality of lenses arranged in a series fashion alonga light axis LT. This lens group 21 includes a focusing lens 211 (seeFIG. 4) for a focal adjustment and the zoom lens 212 (see FIG. 4) forvarying the magnification, and is configured to perform a focaladjustment or magnification variation by driving the focusing lens 211or the zoom lens 212 in the direction of the light axis LT (see FIG. 3).The interchangeable lens 2 also has a lens barrel provided with anoperable ring. The operable ring is disposed at an appropriate sectionon the outer periphery of the lens barrel and is rotatable along theouter peripheral surface of the lens barrel. In response to a manualoperation or an automatic operation, the zoom lens 212 moves in thelight-axis direction in accordance with the rotating direction and therotating amount of the operable ring, thereby setting the zoommagnification (shooting magnification) to a value corresponding to theposition to which the zoom lens 212 is moved.

Internal Configuration of Image Pickup Device 1

An internal configuration of the image pickup device 1 will now bedescribed. FIG. 3 is a vertical sectional view of the image pickupdevice 1. As shown in FIG. 3, the camera body 10 contains, for example,the image pickup element 101 and the EVF 316.

The image pickup element 101 is disposed on the light axis LT of thelens group 21 included in the interchangeable lens 2, when theinterchangeable lens 2 is fitted to the camera body 10, and isorthogonal to the light axis LT. The image pickup element 101 is definedby, for example, a CMOS color area sensor (CMOS-type image pickupelement) having photodiodes constituting a plurality of pixels arrangedtwo-dimensionally in a matrix. The image pickup element 101 generatesanalog electric signals (image signals) of red (R), green (G), and blue(B) color components related to photographic-subject light opticallyreceived via the interchangeable lens 2 and outputs the image signalsfor the R, G, and B colors. A detailed description of the configurationof the image pickup element 101 will be provided later.

A shutter unit 40 is disposed in front of the image pickup element 101in the light-axis direction. The shutter unit 40 is a mechanical focalplane shutter with a curtain that moves in the vertical direction. Withthe opening and closing of the curtain, the shutter opens and closes thelight path of photographic-subject light guided to the image pickupelement 101 along the light axis LT. If the image pickup element 101 isof a complete electronic shutter type, the shutter unit 40 can beomitted.

The EVF 316 includes the liquid crystal panel 310 and an ocular lens106. The liquid crystal panel 310 is, for example, a colorliquid-crystal panel capable of performing image display and is capableof displaying an image picked up by the image pickup element 101. Theocular lens 106 guides a subject image displayed on the liquid crystalpanel 310 outward of the EVF 316. With such a configuration of the EVF316, the user can visually check the photographic subject picked up bythe image pickup element 101.

Electrical Configuration of Image Pickup Device 1

FIG. 4 is a block diagram showing an electrical configuration of theimage pickup device 1. Components shown in FIG. 4 that are the same asthose in FIGS. 1 to 3 are given the same reference numerals. For thesake of convenience, an electrical configuration of the interchangeablelens 2 will be described first.

In addition to the lens group 21 constituting the aforementionedphotographic optical system, the interchangeable lens 2 includes a lensdriving mechanism 24, a lens-position detecting portion 25, a lenscontrol portion 26, and an aperture driving mechanism 27.

In the lens group 21, the focusing lens 211, the zoom lens 212, and anaperture stop 23 for adjusting the amount of light to be incident on theimage pickup element 101 included in the camera body 10 are held in thedirection of the light axis LT (FIG. 3) within the lens barrel. The lensgroup 21 takes in an optical image of a photographic subject so as toform an image on the image pickup element 101. In the AF control mode, afocal adjustment is performed by causing an AF actuator 71M within theinterchangeable lens 2 to drive the focusing lens 211 in the directionof the light axis LT.

A focus-drive control portion 71A is configured to generate a drivecontrol signal for the AF actuator 71M for moving the focusing lens 211to an in-focus position on the basis of an AF control signal receivedfrom a main control portion 62 via the lens control portion 26. The AFactuator 71M is formed of, for example, a stepping motor and applies alens driving force to the lens driving mechanism 24.

The lens driving mechanism 24 is constituted by, for example, a helicoidand a gear (not shown) that rotates the helicoid, and is configured todrive the focusing lens 211 and the like in a direction parallel to thelight axis LT by receiving a driving force from the AF actuator 71M. Themoving direction and the moving distance of the focusing lens 211correspond to the rotating direction and the rotating speed of the AFactuator 71M.

The lens-position detecting portion 25 includes an encoding plate havinga plurality of code patterns formed at a predetermined pitch in thedirection of the light axis LT within the moving range of the lens group21 and an encoder brush that moves together with the lens group 21 whilesliding on the encoding plate, and is configured to detect the movingdistance during a focal adjustment of the lens group 21. A lens positiondetected by the lens driving mechanism 24 is output as, for example, thenumber of pulses.

The lens control portion 26 is defined by a microcomputer containing,for example, a ROM that stores a control program and a memory, such as aflash memory, that stores data related to status information.

The lens control portion 26 has a communication function forcommunicating with the main control portion 62 of the camera body 10 viathe connector Ec. Thus, the lens control portion 26 can sendstatus-information data related to, for example, a focal length of thelens group 21, an exit-pupil position, the aperture, an in-focusdistance, and the amount of ambient light and positional informationrelated to the focusing lens 211 detected by the lens-position detectingportion 25 to the main control portion 62, as well as receive datarelated to, for example, the driving amount of the focusing lens 211from the main control portion 62.

The aperture driving mechanism 27 is configured to change the aperturediameter of the aperture stop 23 by receiving a driving force from anaperture drive actuator 76M via the coupler 75.

An electrical configuration of the camera body 10 will now be described.In addition to the aforementioned image pickup element 101 and theshutter unit 40, the camera body 10 includes an analog front-end (AFE)5, an image processing portion 61, an image memory 614, the main controlportion 62, a flash circuit 63, an operating portion 64, and VRAMs 65(65 a and 65 b). Moreover, the camera body 10 includes a card interface(I/F) 66, the memory card 67, a communication interface (I/F) 68, apower supply circuit 69, the battery 69B, a shutter drive controlportion 73A, a shutter drive actuator 73M, an aperture drive controlportion 76A, and the aperture drive actuator 76M.

The image pickup element 101 is defined by, for example, a CMOS colorarea sensor as mentioned above, and a timing control circuit 51 to bedescribed later controls the image pickup operation, including start(and completion) of an exposure operation of the image pickup element101, output selection of pixels included in the image pickup element101, and reading of pixel signals.

The AFE 5 is configured to apply a timing pulse to the image pickupelement 101 to cause the image pickup element 101 to perform apredetermined operation and is also configured to perform predeterminedsignal processing on image signals output from the image pickup element101 (i.e., a group of analog signals optically received by the pixels ofthe CMOS area sensor), convert the signals into digital signals, andoutput the digital signals to the image processing portion 61. This AFE5 includes the timing control circuit 51, a signal processing portion52, and an A/D converting portion 53.

The timing control circuit 51 generates a predetermined timing pulse(i.e., a pulse that generates, for example, a vertical scan pulse φVn, ahorizontal scan pulse φVm, and a reset signal φVr) on the basis of areference clock output from the main control portion 62 and outputs thetiming pulse to the image pickup element 101 so as to control the imagepickup operation of the image pickup element 101. Moreover, the timingcontrol circuit 51 outputs the predetermined timing pulse to the signalprocessing portion 52 and the A/D converting portion 53 so as to controlthe operation of the signal processing portion 52 and the A/D convertingportion 53.

The signal processing portion 52 is configured to perform predeterminedanalog signal processing on an analog image signal output from the imagepickup element 101. The signal processing portion 52 includes, forexample, a correlated double sampling (CDS) circuit, an auto gaincontrol (AGC) circuit, and a clamping circuit. The A/D convertingportion 53 is configured to convert analog R, G, and B image signalsoutput from the signal processing portion 52 into digital image signalshaving multiple bits (for example, 12 bits) on the basis of the timingpulse output from the timing control circuit 51.

The image processing portion 61 is configured to perform imageprocessing on image data output from the AFE 5 to create an image file,and includes a black-level correcting circuit 611, a white-balancecontrol circuit 612, and a gamma correcting circuit 613. The image datataken in by the image processing portion 61 is temporarily written intothe image memory 614 in synchronization with the reading of the imagepickup element 101. Subsequently, the image data undergoes processing ineach block of the image processing portion 61 by accessing the imagedata written in the image memory 614.

The black-level correcting circuit 611 is configured to correct theblack level of each of the R, G, and B digital image signalsA/D-converted by the A/D converting portion 53 to a reference blacklevel.

The white-balance control circuit 612 is configured to convert the level(adjust the white balance (WB)) of the digital signals for the R, G, andB color components on the basis of a reference white level according toa light source. Specifically, the white-balance control circuit 612specifies a section assumed to be white in the original photographicsubject from brightness and chromatic data in the photographic subjecton the basis of WB adjustment data received from the main controlportion 62, determines an average of the R, G, and B color components inthe aforementioned section, a G/R ratio, and a G/B ratio, and correctsthe level of these values as R and B correction gains.

The gamma correcting circuit 613 is configured to correct the gradationcharacteristics of the WB-adjusted image data. Specifically, the gammacorrecting circuit 613 performs nonlinear conversion and an offsetadjustment on the level of the image data using a gamma correction tablepreliminarily set for each color component.

The image memory 614 is used for temporarily storing image data outputfrom the image processing portion 61 during the photographic shootingmode and is also used as a work area where the main control portion 62performs predetermined processing on the image data. During thereproduction mode, the image memory 614 is used for temporarily storingimage data read out from the memory card 67.

The main control portion 62 is defined by a microcomputer containing,for example, a ROM that stores a control program and a storage portion,such as a RAM, that temporarily stores data, and is configured tocontrol the operation of each portion of the image pickup device 1.

The flash circuit 63 is configured to control the amount of light to beemitted from an external flashlight, connected to the flash portion 318or the connection terminal portion 319, in a flash shooting mode to avalue set by the main control portion 62.

The operating portion 64 includes the mode setting dial 305, thecontrol-value setting dial 306, the shutter button 307, thesetting-button group 312, the cross keypad 314, the push button 315, andthe main switch 317, and is provided for inputting operationalinformation to the main control portion 62.

The VRAMs 65 a and 65 b each have an image-signal storage capacity incorrespondence to the number of pixels in the LCD 311 and the EVF 316and serve as a buffer memory between the main control portion 62 and theLCD 311 and the EVF 316. The card I/F 66 is an interface for sending andreceiving signals between the memory card 67 and the main controlportion 62. The memory card 67 is a storage medium for storing imagedata generated by the main control portion 62. The communication I/F 68is an interface for transmitting, for example, image data to a personalcomputer or other external devices.

The power supply circuit 69 is formed of, for example, a constantvoltage circuit and is configured to generate a voltage for driving theentire image pickup device 1, including a control portion, such as themain control portion 62, the image pickup element 101, and other variouskinds of driving portions. The electricity to be applied to the imagepickup element 101 is controlled by a control signal applied to thepower supply circuit 69 from the main control portion 62. The battery69B is formed of a primary battery, such as an alkaline battery, or asecondary battery, such as a nickel-hydride rechargeable battery, andserves as a power source for supplying power to the entire image pickupdevice 1.

The shutter drive control portion 73A is configured to generate a drivecontrol signal for the shutter drive actuator 73M on the basis of acontrol signal received from the main control portion 62. The shutterdrive actuator 73M is configured to open and close the shutter unit 40.

The aperture drive control portion 76A is configured to generate a drivecontrol signal for the aperture drive actuator 76M on the basis of acontrol signal received from the main control portion 62. The aperturedrive actuator 76M applies a driving force to the aperture drivingmechanism 27 via the coupler 75.

The camera body 10 includes a phase-difference AF calculation circuit 77configured to perform a calculation necessary when performing AF controlusing the image pickup element 101 on the basis of image data, havingundergone black-level correction, output from the black-level correctingcircuit 611.

A phase-difference AF operation of the image pickup device 1 using thephase-difference AF calculation circuit 77 will now be described.

Phase-Difference AF Operation of Image Pickup Device 1

The image pickup device 1 is capable of performing focus detection(phase-difference AF operation) based on a phase-difference detectionmethod by optically receiving light transmitted through sections withdifferent exit pupils in the image pickup element 101. The followingdescription will be directed to the configuration of the image pickupelement 101 and to the principle of a phase-difference AF operationusing the image pickup element 101.

FIGS. 5 and 6 are diagrams for explaining the configuration of the imagepickup element 101.

In the image pickup element 101, focus detection based on aphase-difference detection method is possible in each of AF areas Efarranged in a matrix on an image pickup face 101 f of the image pickupelement 101 (FIG. 5).

Each AF area Ef is provided with normal pixels 110 including R pixels111, G pixels 112, and B pixels 113 in which R, G, and B color filters,respectively, are disposed between photodiodes and micro-lenses ML(denoted by dash lines) functioning as condensing lenses. On the otherhand, as shown in FIG. 6, each AF area Ef is also provided with AF linesLf. In each AF line Lf, AF sensor portions 11 f are arranged along avertical line (vertical direction) of the image pickup element 101. TheAF sensor portions 11 f each achieve a pupil segmentation function byusing a pair of micro-lenses ML1 and ML2 and photoelectric conversionportions PD1 and PD2 (see FIG. 9) for performing a phase-difference AFoperation.

Each AF area Ef also has vertical lines Ln of normal pixels 110 (alsoreferred to as “normal pixel lines”) not having the aforementioned pupilsegmentation function. The normal pixel lines Ln include Gr lines L1 inwhich G pixels 112 and R pixels 111 are alternately arranged in thevertical direction and Gb lines L2 in which B pixels 113 and G pixels112 are alternately arranged in the vertical direction. The Gr lines L1and the Gb lines L2 are alternately arranged in the horizontal directionso that a Bayer arrangement is formed by the normal pixels 110. In eachAF area Ef, image information of a photographic subject is basicallyacquired by the normal pixel lines Ln with a larger number of lines thanthe AF lines Lf.

Furthermore, in each AF area Ef, the AF lines Lf in which the AF sensorportions 11 f each having two micro-lenses ML1 and ML2 with the sameconfiguration (radius and curvature) as the micro-lenses ML of thenormal pixels 110 are repetitively arranged in the vertical directionare formed periodically in the horizontal direction. Normal pixel linesLn (for example, four or more normal pixel lines Ln) serving as acomplement to missing image information of a photographic subject on theAF lines Lf are preferably provided between AF lines Lf that are next toeach other in the horizontal direction. A combination of two normalpixel lines Ln adjacent to the left and right sides of each AF line Lfmay be defined by vertical lines of the same kind (two Gr lines L1 ortwo Gb lines L2) or may be defined by vertical lines of different kinds(one being a Gr line L1 and the other being a Gb line L2).

Before describing the difference between the normal pixels 110 and theAF sensor portions 11 f, the configuration of the normal pixels 110 willbe described first.

FIG. 7 is a vertical sectional view for explaining the configuration ofthe normal pixels 110. An array of the normal pixels 110 shown in FIG. 7corresponds to a Gr line L1 (FIG. 6), which is a normal pixel line Lnformed along the vertical direction (Y direction).

In each normal pixel line Ln, photoelectric conversion portions(photodiodes) PD provided for the respective normal pixels 110 arearranged at a pitch a along the vertical direction (Y direction). Ineach of the normal pixels 110 having a pitch α as a length (width) inthe Y direction, for example, wiring areas We each having a wiringpattern as an electric circuit are provided adjacent to upper and loweredges, as shown in FIG. 8, and a photoelectric conversion portion PDhaving a rectangular shape in plan view is provided. This rectangularphotoelectric conversion portion PD is disposed such that itslongitudinal direction is aligned with the horizontal direction, or inother words, its lateral direction is aligned with the verticaldirection. In addition, as shown in FIG. 7, the neighboringphotoelectric conversion portions PD have a fixed gap β therebetween forensuring the wiring areas We. This gap β is similarly provided betweenthe neighboring photoelectric conversion portions PD in an AF line Lf(see FIG. 9) in which the photoelectric conversion portions PD arearranged in the vertical direction. Specifically, in the image pickupface 101 f serving as a light-receiving portion, a vertical array(vertical line) in which photoelectric conversion portions PD arearranged in the vertical direction (first direction) at a pitch α withthe gaps β maintained therebetween is provided in a plurality in thehorizontal direction (second direction) orthogonal to the verticaldirection, thereby forming a matrix arrangement of photoelectricconversion portions PD.

The micro-lenses ML are provided above the respective photoelectricconversion portions PD in the image pickup face 101 f. The micro-lensesML and the photoelectric conversion portions PD have three metalliclayers therebetween, specifically, a first metallic layer 41, a secondmetallic layer 42, and a third metallic layer 43 in that order from thetop. The second metallic layer 42 and the third metallic layer 43 havelight-blocking properties and serve as wires (linear members) fortransferring electric signals. The second metallic layer 42 and thethird metallic layer 43 are disposed along the horizontal direction (Xdirection) (the wires are disposed along the normal of the plane ofdrawing in FIG. 7). The first metallic layer 41 serves as a groundingsurface for the two metallic layers. Color filters FL are disposed onthe first metallic layer 41, and the micro-lenses ML are provided on thecolor filters FL. Regarding the color filters FL in, for example, anarray of normal pixels 110 arranged in a Gr line L1, green filters Fgand red filters Fr are alternately arranged, as shown in FIG. 7.

In order to prevent the photoelectric conversion portions PD fromreceiving unnecessary light passing through between the micro-lenses ML,the spaces between the micro-lenses ML in each normal pixel line Ln areoptically blocked by the first metallic layer 41. In other words, thefirst metallic layer 41 functions as a layer of a light-blocking maskhaving, for example, octagonal openings OP directly below themicro-lenses ML.

The configuration of the AF sensor portions 11 f will now be described.

FIGS. 9 and 10 are a vertical sectional view and a plan view,respectively, for explaining the configuration of one of the AF sensorportions 11 f. The AF sensor portion 11 f shown in FIGS. 9 and 10 isprovided on one of the AF lines Lf (FIG. 6).

As shown in FIG. 9, the AF sensor portion 11 f includes a photoelectricconversion portion PD1 that optically receives a light beam Ta1 in anupper segment Qa1 of an exit pupil when the interchangeable lens 2 isviewed through an upper (+Y direction side) micro-lens ML1, and aphotoelectric conversion portion PD2 that optically receives a lightbeam Tb2 in a lower segment Qb2 of an exit pupil when theinterchangeable lens 2 is viewed through a lower (−Y direction side)micro-lens ML2. These two photoelectric conversion portions PD1 and PD2have one photoelectric conversion portion PDm disposed therebetween.Similar to the aforementioned normal pixel line Ln (FIG. 7), since theneighboring photoelectric conversion portions PD have a gap βtherebetween, the micro-lenses ML are arranged in view of the gaps β. Indetail, in the AF sensor portion 11 f, a light axis AX1 of themicro-lens ML1 is aligned with an upper edge Ha of the photoelectricconversion portion PD1, and a light axis AX2 of the micro-lens ML2 isaligned with a lower edge Hb of the photoelectric conversion portionPD2. In other words, the light axis AX1 of the micro-lens ML1 isdisposed at a position shifted by a predetermined shift distance La froma center line C1 of a gap β between the photoelectric conversion portionPD1 and an upper neighboring photoelectric conversion portion PD. On theother hand, the light axis AX2 of the micro-lens ML2 is disposed at aposition shifted by a predetermined shift distance Lb from a center lineC2 of a gap β between the photoelectric conversion portion PD2 and alower neighboring photoelectric conversion portion PD. The AF sensorportion 11 f having such a configuration allows for exit-pupilsegmentation by the two photoelectric conversion portions PD1 and PD2optically receiving the light beams Ta1 and Tb2 passing through themicro-lenses ML1 and ML2, respectively.

In each of the AF lines Lf in which the aforementioned AF sensorportions 11 f are arranged, the components disposed above thephotoelectric conversion portions PD, namely, the first to thirdmetallic layers, the color filters, and the micro-lenses, are shifted,relative to the normal pixel lines Ln shown in FIG. 7, by half a pitch(α/2) in the vertical direction (Y direction), and the pairs ofmicro-lenses are also shifted inward. For example, regarding each pairof micro-lenses ML1 and ML2, the light axes AX1 and AX2 thereof arerespectively aligned with the center lines C1 and C2 of the gaps β byshifting the light axes AX1 and AX2, relative to the normal pixel linesLn, by half a pitch, and the light axes AX1 and AX2 are subsequentlyshifted by the shift distances La and Lb (inward) toward thephotoelectric conversion portion PDm in the middle.

Specifically, the arrangement relationship between the two photoelectricconversion portions PD1 and PD2 and the two micro-lenses ML1 and ML2 ineach AF sensor portion 11 f is equivalent to an arrangementconfiguration obtained by relatively shifting specific micro-lenses MLin a normal pixel line Ln that correspond to the micro-lenses ML1 andML2 in the AF sensor portion 11 f by half a pitch α in the verticaldirection relative to the photoelectric conversion portions PD, and thenshifting the aforementioned micro-lenses ML further inward by thepredetermined shift distances La and Lb. The reason the micro-lenses areshifted further by the predetermined shift distances La and Lb is that,if the micro-lenses were to be shifted only by half a pitch, thephotographic-subject light passing through near the center of each exitpupil would enter the wiring areas We, thus lowering the amount of lightto be received by the photoelectric conversion portions PD1 and PD2related to pupil segmentation. In the arrangement configurationdescribed above, a light-blocking section LS (LSp) is provided betweeneach pair of neighboring micro-lenses ML1 and ML2, thereby forming anarray (AF line Lf) of AF sensor portions 11 f. Neighboring AF sensorportions 11 f in each AF line Lf have a light-blocking section LSqprovided therebetween, whose width in the vertical direction (Ydirection) is smaller than that of the light-blocking section LSp. Inthis manner, the AF lines Lf can be formed by slightly changing thedesign of the normal pixel lines Ln, thereby simplifying andfacilitating the design and manufacture of the AF lines Lf. Thefollowing is a detailed description of a light-blocking section LSprovided between neighboring micro-lenses ML in each AF line Lf.

In each AF line Lf, a first metallic layer 44 blocks light at thelight-blocking sections LSp, as shown in FIG. 9, relative to theopenings OP (FIG. 7) in the first metallic layer 41 formed in the normalpixel lines Ln. In detail, two sections OQ1 and OQ2 (FIG. 9)corresponding to where the openings OP in the normal pixel line Ln shownin FIG. 7 are formed are blocked by the first metallic layer 44, and ablack color filter (black filter) Fbp having a width equivalent to abouttwo pixels is placed on the first metallic layer 44. The black filterFbp is placed on the first metallic layer 44 in this manner to minimizethe occurrence of ghost flare. Specifically, if the upper surface of thefirst metallic layer 44 is exposed, light entering from theinterchangeable lens 2 is reflected by the first metallic layer 44 so asto cause ghost flare to occur. Therefore, the black filter Fbp is usedto absorb this reflection light. By blocking light in eachlight-blocking section LSp using the black filter Fbp and the firstmetallic layer 44, the light can be blocked properly and readily. Ineach light-blocking section LSq between neighboring AF sensor portions11 f, a black filter Fbq having a width smaller than that of one pixelis disposed. As a result, in each AF line Lf, black filters Fbp having arelatively large width and black filters Fbq having a relatively smallwidth are alternately and repetitively arranged, as shown in FIG. 10.

Furthermore, in each AF line Lf, transparent filters Ft are employed ascolor filters provided above openings OP1 and OP2 in the first metalliclayer 44. This allows for an increase in the amount of light to bereceived by each AF sensor portion 11 f, thereby achieving highersensitivity.

In each AF sensor portion 11 f, upper wiring sections 45 a and 46 a of asecond metallic layer 45 and a third metallic layer 46, which areclosest to the light axis AX1 of the micro-lens ML1, are positionedcloser towards the light axis AX1 so as to prevent a light beam Tb1 froma lower segment Qb1 of the exit pupil from entering the wiring areas Weas much as possible. Likewise, lower wiring sections 45 b and 46 b ofthe second metallic layer 45 and the third metallic layer 46, which areclosest to the light axis AX2 of the micro-lens ML2, are positionedcloser towards the light axis AX2 so as to prevent a light beam Ta2 froma upper segment Qa2 of the exit pupil from entering the wiring areas Weas much as possible. In other words, the wiring sections 45 a, 45 b, 46a, and 46 b arranged along the horizontal direction (X direction) areprovided near the outer side, in the Y direction, of a line segment Ja(arrow with a solid line) and the outer side, in the Y direction, of aline segment Jb (arrow with a dotted line), as shown in FIG. 9.Specifically, the line segments Ja and Jb respectively connect farthestends of the micro-lenses ML1 and ML2 shown in FIG. 9, which are thefarthest ends from each other in the vertical direction (Y direction),that is, an upper end Ma and a lower end Mb, with the edges Ha and Hb ofthe photoelectric conversion portions PD1 and PD2. The wiring sections45 a, 45 b, 46 a, and 46 b are arranged in this manner to minimize anadverse effect on pupil segmentation. Specifically, if light incident onthe wiring areas We is reflected by the wiring areas We, this reflectionlight may be optically received by the photoelectric conversion portionsPD1 and PD2, possibly causing an adverse effect on pupil segmentation.In addition to the wiring sections 45 a, 45 b, 46 a, and 46 b, dummywiring sections for minimizing incident light on the wiring areas We maybe provided.

With the AF sensor portion 11 f having the above configuration, thelight beam Ta1 from a pupil segment of the exit pupil, that is, theupper segment Qa1 of the exit pupil, travels through the micro-lens ML1and the transparent color filter Ft so as to be optically received bythe photoelectric conversion portion PD1, and the light beam Tb2 fromthe lower segment Qb2 of the exit pupil travels through the micro-lensML2 and the filter Ft so as to be optically received by thephotoelectric conversion portion PD2. In other words, in a matrixarrangement of photoelectric conversion portions PD formed in the imagepickup face 101 f, a specific vertical array, that is, each AF line Lf,is provided with pairs of photoelectric conversion portions PD1 and PD2.The photoelectric conversion portions PD1 and PD2 of each pair opticallyreceive, via the pair of micro-lenses ML1 and ML2, the light beams Ta1and Tb2 of a photographic subject passing through the upper segment Qa1and the lower segment Qb2, which are a pair of segmental regionsdisposed biasedly in opposite directions from each other in the verticaldirection in the exit pupil of the interchangeable lens 2.

In the following description, optical reception data obtained in aphotoelectric conversion portion PD1 will be referred to as “a-seriesdata”, whereas optical reception data obtained in a photoelectricconversion portion PD2 will be referred to as “b-series data”. Forexample, the principle of a phase-difference AF will be described belowwith reference to FIGS. 11 to 15 showing a-series data and b-series dataobtained from a group of AF sensor portions 11 f arranged in a certainAF line Lf (FIG. 6).

FIG. 11 illustrates a simulation result obtained when the focal plane isdefocused towards the near side by 200 μm from the image pickup face 101f of the image pickup element 101. FIG. 12 illustrates a simulationresult obtained when the focal plane is defocused towards the near sideby 100 μm from the image pickup face 101 f. FIG. 13 illustrates asimulation result of an in-focus state in which the focal plane accordswith the image pickup face 101 f. FIG. 14 illustrates a simulationresult obtained when the focal plane is defocused towards the far sideby 100 μm from the image pickup face 101 f. FIG. 15 illustrates asimulation result obtained when the focal plane is defocused towards thefar side by 200 μm from the image pickup face 101 f. In FIGS. 11 to 15,the abscissa axis represents the position of the photoelectricconversion portions PD1 and PD2 in the AF-line-Lf direction, whereas theordinate axis represents an output from the photoelectric conversionportions PD1 and PD2. In FIGS. 11 to 15, graphs Ga1 to Ga5 (shown withsolid lines) each represent a-series data, whereas graphs Gb1 to Gb5(shown with dotted lines) each represent b-series data.

When comparing a-series image sequences represented by a-series graphsGa1 to Ga5 in FIGS. 11 to 15 with b-series image sequences representedby b-series graphs Gb1 to Gb5, it is apparent that a shift amount(displacement amount) occurring in the AF-line-Lf direction (verticaldirection) between an a-series image sequence and a b-series imagesequence increases with increasing defocus amount.

When the relationship between a shift amount between a pair of imagesequences (i.e., a-series image sequence and b-series image sequence)and a defocus amount is made into a graph, a graph Gc shown in FIG. 16is obtained. In FIG. 16, the abscissa axis represents a difference(pixel pitch) between a barycentric position of an a-series imagesequence and a barycentric position of a b-series image sequence,whereas the ordinate axis represents a defocus position (μm). Abarycentric position X_(g) of each image sequence can be determined by,for example, the following equation (1):

$\begin{matrix}{x_{g} = \frac{{X_{1}Y_{1}} + {X_{2}Y_{2}} + \ldots + {X_{n}Y_{n}}}{Y_{1} + Y_{2} + \ldots + Y_{n}}} & (1)\end{matrix}$

In the equation (1), X₁ to X_(n) each denote, for example, the positionof the photoelectric conversion portions PD1 and PD2 from the upper endof the corresponding AF line Lf, whereas Y₁ to Y_(n) each denote anoutput value from the photoelectric conversion portion PD1 or PD2 ateach of the positions X₁ to X_(n).

As shown in the graph Gc in FIG. 16, a difference in barycentricpositions of a pair of image sequences and a defocus amount have aproportional relationship. This relationship can be expressed by thefollowing equation (2) in which the defocus amount is denoted by DF (μm)and the difference in barycentric positions is denoted by C (μm).DF=k×C  (2)

In the equation (2), a coefficient k represents a gradient Gk (shownwith a dotted line) with respect to the graph Gc in FIG. 16 and can bepreliminarily obtained from, for example, factory tests.

Accordingly, after using the phase-difference AF calculation circuit 77to determine a difference in barycentric positions (phase difference)related to a-series data and b-series data obtained by an AF sensorportion 11 f, a defocus amount is calculated using the equation (2). Byapplying a driving amount equivalent to the calculated defocus amount tothe focusing lens 211, automatic-focus (AF) control for moving thefocusing lens 211 to a detected focal position can be performed. Therelationship between the aforementioned defocus amount and the drivingamount for the focusing lens 211 is uniquely determined on the basis ofa design value of the interchangeable lens 2 fitted to the camera body10.

In the image pickup device 1, the image pickup element 101 is providedwith the AF sensor portions 11 f for a phase-difference AF operation andeach including a pair of photoelectric conversion portions PD1 and PD2with the same size as the photoelectric conversion portions PD in thenormal pixel lines Ln, a pair of micro-lenses ML1 and ML2, and a firstmetallic layer 44 having openings OP1 and OP2 with about the same sizeas the micro-lenses ML1 and ML2 directly below the micro-lenses ML1 andML2. Thus, the image pickup element (that is, an image pickup elementhaving a phase-difference detecting function) 101 is capable ofaccurately performing focus detection based on a phase-differencedetection method and can also be manufactured satisfactorily even aspixels become miniaturized. As compared with an image pickup elementhaving a phase-difference detecting function discussed in JapaneseUnexamined Patent Application Publication No. 2005-303409 in which pupilsegmentation is implemented by limiting photographic-subject light usingsmall openings in a metallic layer (light-blocking mask), blockage ofnecessary light beams can be minimized in this embodiment, therebyreducing degradation of the sensitivity of the photoelectric conversionportions PD1 and PD2. Furthermore, in the image pickup element having aphase-difference detecting function discussed in Japanese UnexaminedPatent Application Publication No. 2005-303409, since the metallic layerhaving the small openings are projected from above the photoelectricconversion portions and are thus exposed, the exposed metallic layer canpossibly cause ghost flare to occur. In contrast, since black filters Fbare disposed on the first metallic layer 44 in the image pickup element101 according to this embodiment, the occurrence of ghost flare can beprevented.

The micro-lenses ML1 and ML2 in each AF sensor portion 11 f are disposedsuch that the respective light axes AX1 and AX2 thereof extend throughthe edges Ha and Hb, which are the farthest edges from each other in thevertical direction (Y direction), of the photoelectric conversionportions PD1 and PD2, as shown in FIG. 9. As a result, even if thephotoelectric conversion portions PD are disposed with a gap βtherebetween in the corresponding AF line Lf to ensure the wiring areasWe, light beams traveling through near the center of the exit pupils canbe optically received by the photoelectric conversion portions PD1 andPD2, thereby minimizing output reduction of the photoelectric conversionportions PD1 and PD2 and allowing for a highly reliable phase-differenceAF operation.

Since the photoelectric conversion portions PD1 and PD2 in each AFsensor portion 11 f are two neighboring photoelectric conversionportions PD with one photoelectric conversion portion PDm disposedtherebetween in the corresponding AF line Lf, as shown in FIG. 9, the AFsensor portion 11 f can be properly formed even with a pixel line of theimage pickup element 101 in which the photoelectric conversion portionsPD are arranged with the gap β maintained therebetween. When differentAF lines (sometimes referred to as “second AF lines” hereinafter)extending in a different direction, for example, the horizontaldirection (X direction), from that of the AF lines Lf (sometimesreferred to as “first AF lines” hereinafter) are provided, theaforementioned photoelectric conversion portions PDm may be disposed atthe intersections between the first AF lines and the second AF lines sothat a continuous line output can be attained without having to dividethe AF lines.

Modifications

As an alternative to the above embodiment that employs the AF areas Efhaving the AF lines Lf including the micro-lenses ML1 and ML2 with thesame configuration as those in the normal pixels 110, as shown in FIG.6, AF areas Efa having AF lines Lfa that include micro-lenses MLa andMLb with a larger diameter than that of the micro-lenses in the normalpixels 110, as shown in FIG. 17, may be employed. In that case, thefirst metallic layer 44 is provided with openings with dimensions set inaccordance with the diameter of the micro-lenses MLa and MLb,specifically, openings somewhat larger than the openings OP1 and OP2shown in FIG. 9. With these micro-lenses MLa and MLb (and the openingsin the first metallic layer 44), the sensitivity of AF sensor portions11 fa in the AF lines Lfa can be enhanced.

As an alternative to the above embodiment that employs the AF areas Efhaving the AF lines Lf including the light-blocking sections LS eachoccupying the entire area between each pair of micro-lenses ML1 and ML2separated from each other by a distance equivalent to one pixel or more,as shown in FIG. 6, AF areas Efb with AF lines Lfb each having a normalpixel 110, such as a G pixel 112, interposed between a pair ofmicro-lenses ML1 and ML2, as shown in FIG. 18, may be employed. In thatcase, light-blocking sections LSa and LSb are formed in areas between apair of micro-lenses ML1 and ML2 and a normal pixel 110. With thisconfiguration, missing image information of a photographic subject inthe AF lines can be reduced by the normal pixels 110 interposed in theAF lines Lfb, and improved image quality can be achieved by acomplementation process using image information acquired by these normalpixels 110.

As an alternative to the above embodiment that employs the AF areas Efhaving the AF lines Lf constituted only by the AF sensor portions 11 f,as shown in FIG. 6, AF areas Efc having AF lines Lfc in which normalpixels 110 are interposed between neighboring AF sensor portions 11 f,as shown in FIG. 19, may be employed. In that case, image information ofthe normal pixels 110 in the AF lines Lfc can be used as a complement tomissing image information of a photographic subject in the AF sensorportions 11 f, thereby achieving improved image quality.

In the above embodiment, the central photoelectric conversion portionPDm interposed between the pair of photoelectric conversion portions PD1and PD2 in each AF sensor portion 11 f shown in FIG. 9 may alternativelybe omitted. In detail, as in an AF sensor portion 11 fd shown in FIG.20, instead of providing a photoelectric conversion portion between apair of photoelectric conversion portions PD1 and PD2, a light-blockingsection LSr disposed between a pair of micro-lenses ML1 and ML2 may beshortened by a length equivalent to one pixel relative to thelight-blocking section LSp shown in FIG. 9. In consequence, as in an AFarea Efd shown in FIG. 21, AF lines Lfd are formed such that thedistance between each pair of micro-lenses ML1 and ML2 is reduced,thereby improving the accuracy of pupil segmentation.

As an alternative to the image pickup element 101 according to the aboveembodiment that employs the AF sensor portions 11 f in which the firstmetallic layer 44 covers the underside of the black filters Fbp, asshown in FIG. 9, AF sensor portions life each having an opening OPm in asection of a first metallic layer 44 a directly below the black filterFbp, as shown in FIG. 22, may be employed. In that case, the blackfilter Fbp preferably has low transmittance (of, for example, 3% orlower) to reduce the amount of light passing through the black filterFbp to be optically received by the photoelectric conversion portion PDmdisposed directly therebelow.

On the other hand, in the above embodiment, the black filters Fbp andFbq in the configuration shown in FIG. 9 may be omitted. In that case,even though the aforementioned first metallic layer becomes exposed andthere is a concern that ghost flare may occur, this can be prevented by,for example, coloring the upper surface of the first metallic layer inblack or using a conductive layer composed of a black conductivematerial as the first metallic layer.

Although the image pickup element 101 having the AF lines Lf is providedin a single-reflex-type digital camera in the above embodiment, theimage pickup element 101 may alternatively be provided in a compact-typedigital camera.

Although the AF sensor portions in the above embodiment are eachprovided with transparent color filters above the openings OP1 and OP2in the first metallic layer 44, the AF sensor portions may alternativelybe provided with green color filters with high visibility in view ofbetter focusing accuracy, or may be provided with red or blue colorfilters.

Although the light axes AX1 and AX2 of the micro-lenses ML1 and ML2 ineach AF sensor portion in the above embodiment are exactly aligned withthe upper edge Ha of the photoelectric conversion portion PD1 and thelower edge Hb of the photoelectric conversion portion PD2, respectively,as shown in FIG. 9, the light axes AX1 and AX2 may be slightlymisaligned with the edges Ha and Hb. In other words, the light axes AX1and AX2 of the micro-lenses ML1 and ML2 may be disposed to extendthrough the vicinities of the upper edge Ha and the lower edge Hb of thephotoelectric conversion portions PD1 and PD2.

The embodiments of the present invention described above are onlyexamples and are not intended to limit the invention. Countlessmodifications not described above are permissible insofar as they arewithin the scope of the invention.

1. An image pickup element comprising: a light-receiving portion having a matrix arrangement of photoelectric conversion portions, the matrix arrangement being formed by disposing a plurality of first-direction arrays, each having photoelectric conversion portions arranged in a first direction with a predetermined gap maintained therebetween, in a second direction that is orthogonal to the first direction; and a plurality of micro-lenses provided above the light-receiving portion, wherein a certain first-direction array in the matrix arrangement of photoelectric conversion portions is provided with a pair of photoelectric conversion portions that optically receive, via a pair of micro-lenses, photographic-subject light beams passing through a pair of segmental regions in an exit pupil of a photographic optical system, the pair of segmental regions being disposed biasedly in opposite directions from each other in the first direction, and wherein the pair of micro-lenses is disposed such that light axes thereof extend through vicinities of edges of the pair of photoelectric conversion portions, the edges being the farthest edges from each other in the first direction.
 2. The image pickup element according to claim 1, wherein the predetermined gap has electrical wiring formed therein.
 3. The image pickup element according to claim 1, wherein the pair of photoelectric conversion portions includes two neighboring photoelectric conversion portions disposed on opposite sides of one photoelectric conversion portion in the certain first-direction array.
 4. The image pickup element according to claim 1, wherein the photoelectric conversion portions arranged in the matrix arrangement have a rectangular shape in plan view, and wherein the first direction is a lateral direction of each photoelectric conversion portion.
 5. The image pickup element according to claim 1, wherein linear members having light-blocking properties and disposed along the second direction are provided near outer sides, in the first direction, of line segments that respectively connect ends of the pair of micro-lenses, which are the farthest ends from each other in the first direction, with the farthest edges.
 6. An image pickup device comprising: a photographic optical system; and an image pickup element configured to optically receive photographic-subject light passing through an exit pupil of the photographic optical system, wherein the image pickup element includes a light-receiving portion having a matrix arrangement of photoelectric conversion portions, the matrix arrangement being formed by disposing a plurality of first-direction arrays, each having photoelectric conversion portions arranged in a first direction with a predetermined gap maintained therebetween, in a second direction that is orthogonal to the first direction; and a plurality of micro-lenses provided above the light-receiving portion, wherein a certain first-direction array in the matrix arrangement of photoelectric conversion portions is provided with a pair of photoelectric conversion portions that optically receive, via a pair of micro-lenses, photographic-subject light beams passing through a pair of segmental regions in the exit pupil, the pair of segmental regions being disposed biasedly in opposite directions from each other in the first direction, and wherein the pair of micro-lenses is disposed such that light axes thereof extend through vicinities of edges of the pair of photoelectric conversion portions, the edges being the farthest edges from each other in the first direction. 